Never heard of these --makes sense, in that engines have basic meters/alarms for oil pressure and temp...so, why not cooling water flow, in case you suck up a plastic bag, etc. in the raw water seacock, or impeller vane breaks. Seems like it would let you know about the problem before overheat occurs, and allow you to isolate it to lack of water flow.

I'm leery of bells and whistles and complicating systems, but this is intriguing. My question would be, how much does it restrict water flow in the system when plumbed in line! Apparently, you can set it to alarm at a specified flow rate (i.e., if it drops below the engine spec flow rate). Fairly cheap, at about $65. Anyone here have any experience with these?

Not sure where in the raw water system you'd install it, though. The model for 15 - 40 HP engines has 1" ports, so maybe in the hose before the raw water pump? Or in the vented loop hose? I couldn't fit it anywhere else on my engine, but not sure it would make the most sense to have it.

Product description reads:

Features:

# Monitors the flow of raw cooling water to engines, generators, or bait tanks
# Prevents costly engine damage
# Patented design for marine use
# Sets off alarm when flow rate falls below minimum (adjustable)
# Can be used with bell alarm (20100) or horn alarms (20106)